Underreading errors, or false-negatives, are the most frequent and costly type of error occurring in diagnostic radiology. A subset of these underreading errors have been attributed to "satisfaction of search" which occurs when lesions present remain undetected following the detection of an initial lesion in a rediograph. However, no one has ever demonstrated that such undetected lesions would be discovered if the initially detected lesion were somehow removed from the radiograph. In the proposed experiments, we measure detection accuracy for lesion before and after the addition of a moderately obvious nodular lesion in order to demonstrate rigorously satisfaction of search. The experiments are designed so as to maximize our opportunity for observing the satisfaction effect. If we succeed in documenting the effect, our method will serve as a paradigm permitting futher experiments to be conducted. We will also attempt to determine whether different types of lesions (e.g., of the lung; mediastinum, chest wall, etc.) are affected differentially by the presence of the simulated nodule. In our second experiment, we measure the inspection time for true- and false-positives and the inspection time between the last response and the termination of search. These measurements will allow us to begin to explain any satisfaction effect which results in terms of perceptual capture and/or prematurely halted search. By studying underreading error in the presence of multiple abnormalities, the causes of these interpretive failures may be understood and corrected.